Due to their excellent mechanical strength, heat resistance, electrical properties, dimensional stability, flame retardancy, transparency and so on, polycarbonate-based resins are widely used for electrical, electronic and OA appliances, optical media, automobile components, building components, etc.
Such polycarbonate-based resins are generally produced by the interface process for direct reaction between bisphenol A (aromatic dihydroxy compound) and phosgene or by the melt process for transesterification reaction (polycondensation reaction) between bisphenol A and diphenyl carbonate (carbonic acid diester) in molten state, etc.
However, molded objects obtained from these polycarbonate-based resins produced by using bisphenol A as an aromatic dihydroxy compound do not have sufficient surface hardness for use in outdoor applications, e.g., automobile head lamps, spectacle lenses, sheets and so on.
For this reason, polycarbonate-based resins may be provided with a hard coat layer or the like on their surface to improve their surface hardness.
However, to provide a hard coat layer or the like on the surface, the production process requires one more step, so that the production efficiency will be reduced. Further, in the case of molded objects having complicated shapes, it is difficult to provide a hard coat layer on their surface.
Many studies have now been conducted to blend polycarbonate-based resins with a particular type of resin in an attempt to improve their surface hardness while maintaining their transparency. There are proposed many cases where acrylic resins, which are transparent as in the case of polycarbonate-based resins, are used as resins to be blended with polycarbonate-based resins. For example, Patent Documents 1 and 2 disclose resin compositions each comprising a polycarbonate-based resin and an acrylic resin whose molecular weight is within a particular range.
Moreover, there are also proposed cases where acrylic copolymers are blended with polycarbonate-based resins. For example, Patent Documents 3 to 7 disclose resin compositions each comprising a polycarbonate-based resin and a (meth)acrylic copolymer.